1. Field of the Invention
The present invention relates generally to apparatus for perforating wells, and more particularly, to apparatus for perforating wells comprised of one or more encapsulated shaped charges held by a wire or strip carrier.
2. Description of the Prior Art
A variety of apparatus have heretofore been developed and used for forming openings known as perforations in wells which extend from the well bores into subterranean formations penetrated thereby. Generally, the perforating apparatus is assembled with a plurality of shaped explosive charges and lowered in a well bore to a position adjacent a subterranean formation to be perforated. Upon the detonation of the shaped charges, elongated explosive jets are formed which produce perforations through any casing, liner, cement, or the like in the well bore and into the subterranean formation adjacent the well bore. The perforations form flow passages through which hydrocarbons flow from the subterranean formation into the well bore.
Well perforating apparatus have heretofore been comprised of a plurality of encapsulated shaped charges held in spaced relationship one above the other by wires or metal strips. Such perforating apparatus is most often used where it is necessary or desirable to lower the perforating apparatus in the well bore through a relatively small diameter tubing string already disposed in the well bore. The shaped charges generally include a closed ignition end and an open discharge end. A cap is sealingly attached over the discharge end, and the thus encapsulated shaped charges are attached to a wire or metal strip carrier by attachment means formed on the charges.
Wire carriers have heretofore been comprised of two pairs of substantially parallel wires having adjacent bends formed therein at intervals therealong for accepting complementary structure including wire containing cavities formed at the ignition and capped discharge ends of the encapsulated shaped charges. Metal strip carriers are comprised of elongated metal strips having threaded openings spaced therealong for receiving complementary threaded extensions at the capped discharge ends of the encapsulated shaped charges.
Depending upon the particular type of well being perforated, the characteristics of the subterranean formation and other factors including the well operator's preference, either a wire carrier or a metal strip carrier may be utilized in perforating any particular well. As a result, it has heretofore been necessary for the perforating apparatus operator to have available both encapsulated shaped charges adapted for attachment to a wire carrier, i.e., charges having structure formed at the ignition and capped discharge ends containing cavities for receiving wires, and encapsulated shaped charges adapted for attachment to a metal strip carrier, i.e., charges having complementary threaded structure at the capped discharge ends thereof.
By the present invention, an improved apparatus for perforating wells is provided comprised of an encapsulated shaped charge which can optionally be used with either wire or metal strip carriers.